The present invention relates to a benzidine derivative suitable for an electric charge transferring material in a photosensitive material, and also relates to a photosensitive material using such a derivative.
As a photosensitive material in an image forming apparatus such as an electrophotographic copying apparatus, there has recently and widely been used an organic photosensitive material which is excellent in machinability and advantageous in production cost and which offers a great degree of freedom for design of performance.
For forming a copied image with the use of a photosensitive material, the Carlson process is widely used. The Carlson process comprises the steps of uniformly charging a photosensitive material with electricity by corona discharge, exposing the charged photosensitive material to a document image, thereby to form an electrostatic latent image corresponding to the document image, developing the electrostatic latent image by a toner containing developer, thereby to form a toner image, transferring the toner image to paper or the like, fixing the toner image thus transferred, and cleaning the photosensitive material to remove toner remaining thereon after the toner image has been transferred. To form an image of high quality in the Carlson process, it is required that the photosensitive material is excellent in charging and photosensitive characteristics and presents a low residual potential after exposed to light.
Conventionally, there have been known inorganic photoconductive materials such as selenium, cadmium sulfide and the like as photosensitive materials. However, these inorganic photoconductive materials are toxic and need great production costs.
There has been proposed a so-called organic photosensitive material using various organic substances in place of the above-mentioned inorganic substances. Such an organic photosensitive material has a photosensitive layer comprised of an electric charge generating material for generating electric charges by light exposure and an electric charge transferring material having a function of transferring the electric charges thus generated.
To meet various requirements for the organic photosensitive material, it is necessary to properly select the electric charge generating material and the electric charge transferring material. As the electric charge transferring material, there have been proposed and put on the market benzidine derivatives such as 4,4'-bis[N-phenyl-N-(3-methylphenyl)amino]diphenyl, 4,4'-bis[N,N-di(4-methylphenyl)amino]-2,2'-dimethyl diphenyl, 4,4'-bis[N,N-di(4-methylphenyl)amino]-3,3'-dimethyl diphenyl and the like (see Japanese Unexamined Patent Publication Nos. 144558/1982 and 62038/1986, U.S. Pat. Nos. 4,047,948 and 4,536,457, Japanese Unexamined Patent Publication Nos. 124949/1986, 134354/1986, 134355/1986 and 112164/1987).
However, the electric charge transferring material comprised of the benzidine derivative has insufficient electron donating properties and electric charge transferring ability. When forming a photosensitive material, the electric charge transferring material has insufficient sensitivity and a great residual potential.